2181638 has 4 divisors (see below), whose sum is σ = 3272460. Its totient is φ = 1090818.

The previous prime is 2181629. The next prime is 2181649. The reversal of 2181638 is 8361812.

It is a semiprime because it is the product of two primes.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 2181638.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 545408 + ... + 545411.

It is an arithmetic number, because the mean of its divisors is an integer number (818115).

2^2181638 is an apocalyptic number.

2181638 is a deficient number, since it is larger than the sum of its proper divisors (1090822).

2181638 is a wasteful number, since it uses less digits than its factorization.

2181638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1090821.

The product of its digits is 2304, while the sum is 29.

The square root of 2181638 is about 1477.0368986589. The cubic root of 2181638 is about 129.6962930023.

The spelling of 2181638 in words is "two million, one hundred eighty-one thousand, six hundred thirty-eight".